1. Field of the Invention
The present invention relates to a control system for the detection of leaks in insulation-jacketed pipes having measuring probes, each with two electrodes, arranged at sectional intervals and connected to an evaluation circuit.
A control system featuring a measuring conductor in the form of a high-frequency conductor is described in the German Offenlegungsschriften (Publ. Applications) No. 26 19 042 and No. 27 25 224. In the event of leakage, a foil separating the conductors is damaged, so as to alter the attenuation characteristics of the measuring conductor.
A control system of the type described in the introduction is described in U.S. Pat. No. 3,882,382. There, the measuring probe constitutes part of the insulating jacket. The electrodes are connected to an electrical voltage. Leaking fluid is intended to cause a change in the resistance between the electrodes. In connection with the leak detection on steam pipes, it is necessary to fill the space between the electrodes with an electrolyte. Such a control system is unreliable in its response behavior. The use of an electrolyte may lead to malfunction caused by ambient humidity. Furthermore, it may be difficult to ascertain the failure of a measuring probe. A similar control system is described in the German Gebrauchsmuster (Utility Patent) No. 80 11 887. There, leaking fluid is intended to change the resistance of a measuring conductor.